Should the pulleys be able to move freely (that is, by hand while the car is NOT under power at all) once the belt is on completely? If none of the pulleys can rotate at all by hand, does that mean the belt is on too tight?

 

Ok. I assume you got the belt on. If so, tighten the belt properly. There are two ways in doing so. The tedious deflection method, explaned in the FSM or haynes, or by the good ol' 90^ method. The 90 degree works great and is the easiest. Just twist the belt at the midpoint between the crank pulley and AC pulley, you should not be able to go more than 90 degrees while using moderate to excess thumb pressure.

Whether or not the pullies can turn freely is pretty irrevelant if you tighten the belt correctly.

 

Make sure you do this step. Overtightening will cause premature bearing wear aka "marbles-in-a-can" noise. Been there, done that.

 

How would I know if I have OVER-tightened?

 

Like Wizard posted, if you can twist it 90 degress then your good, if you cannot twist its too tight, any more then the 90 degrees too loose.

 

I wouldnt say more than 90 degrees is too loose. How about able to twist 90 with out extreme or excess force. If it can twist just past 90 your in good shape. I also test it from the top right at the blower pulley but that is for the advanced s/c guys.. haha j/k. Really I do check it from there as well on a daily basis.